Revert ktlint update, unrevert Gradle and PR build workflow reverts (#3681)

.github/workflows/pr_build_check.yml

@@ -0,0 +1,18 @@
+name: Pull request build check
+on: [pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Clone repo
+        uses: actions/checkout@v2
+      - name: Set up JDK 1.8
+        uses: actions/setup-java@v1
+        with:
+          java-version: 1.8
+      - name: Install NDK
+        run: sudo ${ANDROID_HOME}/tools/bin/sdkmanager --install "ndk;21.0.6113669"
+      - name: Build project
+        run: ./gradlew assembleDebug